Haemodialysis or peritoneal dialysis devices are known in various versions. The exchange of substances between the blood and the dialysis fluid takes place in a dialyzer which has a first flow path for the blood and a second flow path for the dialysis fluid, wherein both flow paths are normally separated from each other by a semi-permeable membrane. The first flow path is part of an extracorporeal blood circulation system with a feed line and a return line for the blood and also additionally a pump supporting the blood flow. The second flow path is connected to equipment feeding and removing the dialysis fluid.
In addition to the so-called single-path systems in which the continuously fed dialysis fluid passes through the dialyzer only once and is then discarded, so-called batch systems are known. U.S. Pat. No. 4,610,782 describes such a haemodialysis device, which operates with a fixed-volume container sealed off from the atmosphere, which is completely filled with fresh dialysis fluid prior to the start of the treatment. During operation, the fluid is pumped out of the container through the dialyzer and the used fluid is passed back into the container.
Fresh and used dialysis fluid are prevented from mixing in the case of the known haemodialysis device by removing the dialysis fluid in the upper area of the container and returning it in the lower container area. Underlaying the fresh dialysis fluid with the used dialysis fluid remains stable through the maintaining of a vertical temperature gradient in the container from top to bottom.
The container consists of glass which, because of the pore-free surface, is superior with regard to hygiene and bacteriology compared to other materials. In addition, glass is largely resistant to chemicals coming into consideration, can be satisfactorily cleaned and is physiologically harmless. However, such a repeatedly re-usable glass container proves to be disadvantageous because the glass container needs to be disinfected before the renewed dialysis, treatment.
U.S. Pat. No. 4,767,526 likewise describes a dialysis device in which the dialysis fluid is provided in a container. In order to avoid disinfection, it is proposed to line the container with a flexible bag, which is discarded after use.
Flexible plastic bags which consist of two films lying flat one over the other and welded together at their edges are known as containers for holding medical fluids.
DE 198 251 58 C1 likewise describes a disposable bag for a haemodialysis device or a device for peritoneal dialysis which preferably has a concentrate for the preparation of dialysis fluid. This bag can consist of a chamber in which the used fluid is layered underneath the fresh dialysis fluid in the course of the dialysis process. Alternatively, the disposable bag can also contain a film which divides the bag into two chambers, wherein the fresh dialysis fluid is present in one chamber of the bag and the used fluid is passed into the other chamber during the dialysis process.
A disadvantage of the above-named glass containers is that a rapid re-use is not possible because of the laborious disinfection step. However, disposable bags, which do not have this disadvantage, have not yet solved the problem that in the case of introduced granular material to be dissolved in water the different constituents of the granular material react with each other during the storage of the bag including granular material, with the result that there is no storage stability over a certain period of time. In addition, dialysis fluids which are prepared by dissolving granular material which contains all the necessary constituents often have the problem that, as a result of an undesired reaction of different constituents, not all of the granular material dissolves. Both problems before-mentioned often lead to a degradation or agglomeration of at least one of the concentrates provided. Furthermore, it is important to correspondingly control the pH while the solvent is being poured into the bag with granular material, so that undesired precipitations are avoided during the dissolution of the granular material in the fluid. If the named problems occur, the dialysis fluid is not suitable for haemodialysis or peritoneal dialysis and must be discarded together with the bag.
In addition to glucose, or other ingredients which are not able to contribute to the electric conductivity of a fluid, and physiologically essential salts, or ions, dialysis fluids must have a pH in the neutral range. A pH in the neutral range is set by adding an acid and a basic component. These acid and basic components must necessarily be physiologically compatible. Therefore, carbonate salts, e.g., sodium hydrogen carbonate, are preferably used as basic buffer component. The solution must contain calcium and magnesium ions, in addition to sodium and potassium ions, as physiologically essential ions. A dialysis fluid is most often prepared from a single concentrate, which is introduced in the inlaid bag in the case of DE 198 25 158. If such concentrates which contain readily soluble calcium or magnesium salts and, as basic buffer component, a (bi)carbonate salt are stored for prolonged time, then the problem arises, at least under atmospheric humidity conditions, that the components can react with each other and thus form poorly soluble calcium or magnesium carbonate. Likewise, poorly soluble calcium or magnesium carbonate precipitates from a solution the pH of which is not set in the ideal range of preferably <pH 8. It is therefore disadvantageous to introduce a concentrate with all the necessary physiologically essential components in a bag together, since such systems cannot be stored for long because of the above-named problems and, further, because during dissolution in a fluid, sections of the solution have a pH greater than 8, with the result that undesired precipitations occur.